The primary roof support systems used in coal mines include headed rebar bolts typically 4 feet to 6 feet in length, ¾ inch and ⅝ inch in diameter, and used in conjunction with resin grouting in 1 inch diameter holes.
Multi-compartment resin cartridges are used to supply the resin grouting for the support systems. Among the cartridges known for this purpose are those disclosed in U.S. Pat. No. 3,795,081 to Brown, Jr. et al., U.S. Pat. No. 3,861,522 to Llewellyn et al., U.S. Pat. No. 4,239,105 to Gilbert, and U.S. Pat. No. 7,681,377 B2 to Simmons et al., the entire contents of each being incorporated herein by reference thereto. Cartridges typically are available in a variety of lengths ranging from 2 feet to 6 feet and in diameter from ¾ inch to ¼ inch. The cartridges also typically include two compartments: a first compartment with a reinforced, thixotropic, polyester resin mastic (a fluid) therein, and a second compartment with an organic peroxide catalyst (also a fluid) therein. The resin and catalyst are segregated from one another in order to prevent a reaction prior to puncturing of the compartments to allow contact and mixing to occur.
In use, a cartridge and bolt (or other reinforcing member) are placed in a borehole so that they abut one another. In order to puncture the cartridge so that the contents of the compartments may be released and mixed, the bolt for example may be rotated in place to shred the cartridge, thereby mixing the components and permitting solidification of the mastic. Mixing of the resin and catalyst (due to cartridge rupture as well as spinning of the bolt in the borehole) results in hardening that allows the bolt to be held in place.
When multi-compartment resin cartridges are manufactured, such as in the form of partitioned film packages, a series of cartridges may be formed using a package-forming apparatus. The cartridges may be separated from one another at a clipping head associated with the package-forming apparatus, where the cartridges are cut from one another and sealed. Alternatively, a series of cartridges may be separated from one another in a different operation from the cartridge forming operation, i.e., off-line using a cutter separate from the clipping head. In particular, the cartridges may be separated from one another proximate their clipped ends, i.e., proximate the regions of the opposite ends of the cartridges which are each clipped so as to retain the resin and catalyst in the package. Thus, before being separated, adjacent cartridges have two clips adjacent each other with some cartridge packaging disposed therebetween. A cut is made between the adjacent clips to separate the cartridges.
U.S. Pat. No. 4,616,050 to Simmons et al. discloses filler-containing hardenable resin products. In particular, a hardenable resin composition is disclosed that is adapted for use in making set products, e.g., a hardened grout for anchoring a reinforcing member in a hole. A course/fine particulate inert solid filler component, e.g., limestone and/or sand, is used. In one composition, a resin component and a catalyst component are provided in a 70:30 percentage ratio. In one example, the resin component is describes as a mixture of 21% of a resin formulation and 79% filler (limestone or limestone in combination with sand). The base resin formulation consisted approximately of 64.0% of a polyester resin, 17.1% styrene, 14.2% vinyl toluene, 1.9% fumed silica, and 2.9% stabilizers and promoters. The polyester resin was the esterification product of maleic anhydride, propylene glycol, and diethylene glycol, the maleic anhydride having been partially replaced with phthalic anhydride (30% maleic anhydride, 23% phthalic anhydride, 17% propylene glycol, and 30% diethylene glycol). The catalyst component was a mixture of 72.5% filler (i.e., limestone), 19.1% water, 0.4% of methylcellulose, and 8.0% of a benzoyl peroxide (BPO) catalyst paste consisting, approximately, of 49.3% BPO, 24.7% butyl phenyl phthalate, 14.8% water, 7.9% polyalkylene glycol ether, 2.0% zinc stearate, and 1.3% fumed silica. Two grades of limestone were used as specified in Table A, and both “coarse” and “fine” filler particles were used. Examples of disclosed compositions are as follows:
TABLE AProductFillerProduct IFiller in Resin: [12.5% coarse particles and 87.5% fineparticles]38% “Grade A” limestone:33% of the particles averaged larger than 1.19 mm (with10% of these larger than 2.3 mm, 3% larger than 4.76 mm,and none larger than 9.53 mm); an average of 42% of theparticles were smaller than 0.59 mm (with 17% smallerthan 0.297 mm, and 5% smaller than 0.149 mm)62% “Grade B” limestone:an average of 99.8% of the particles were smaller than0.84 mm, with 98.7% smaller than 0.297 mm, 97.9%smaller than 0.250 mm, 91.5% smaller than 0.149 mm, and69.6% smaller than 0.074 mmFiller in Catalyst:100% Grade B limestoneProduct IIFiller in Resin: [31.9% coarse particles and 68.1% fineparticles]38% sand:83.9% of the particles averaged larger than 1.00 mm(with 59.6% of these larger than 1.19 mm); 6.6% of theparticles averaged smaller than 0.84 mm (with 1.9%smaller than 0.59 mm, 0.8% smaller than 0.42 mm, and0.2 smaller than 0.297 mm)62% Grade B limestoneFiller in Catalyst:100% Grade B limestoneProduct IIIFiller in Resin:100% Grade B limestoneFiller in Catalyst:100% Grade B limestoneProduct VFiller in Resin: [12.4% coarse particles, 87.6% fineparticles]37.5% Grade A limestone62.5% Grade B limestoneFiller in Catalyst:100% Grade B limestoneProduct VIFiller in Resin:62.5% Grade B limestone37.5% coarse sandall particles passed through a 3.18-mm screen and wereheld on a 1.59-mm screenFiller in Catalyst:100% Grade B limestone
As used herein, the terms “grouting,” “grouting system,” “grout,” and “grout system” mean a substance that hardens to anchor a reinforcing member in a space. For example, grouting can be provided in the form of a cartridge with a compartment housing a polyester resin and a compartment housing an initiator/catalyst, such that when the cartridge is shredded and the resin is mixed with the initiator/catalyst, a reinforcing member can be anchored in a space.
In manufacturing grouting, from a materials cost perspective, as more filler is used the cost becomes less expensive. In other words, the more filler used instead of actual resin or catalyst, the less expensive the materials required to form the composition. Moreover, filler permits better performance to be achieved by increasing the strength of the hardened grout. However, the tradeoff with using more filler in a composition is that the composition becomes more viscous. For example, the more that filler is used in the resin, the more difficult it is to pump the resin mastic into the package (cartridge) because the resin becomes “thick” (the viscosity increases). High resin mastic pumping pressures become necessary with such high viscosity compositions. Also, the more that filler is used in the overall grouting composition, the more difficult it becomes for the mine bolt to be able to penetrate the cartridge when spun.
In basic principle, when larger (e.g., coarse) filler particles are used in a composition, the particles overall provide lower surface area than when smaller (e.g., fine) particles are used. Use of such larger particles thus permits a lower viscosity grouting and advantageously aids in shredding of the cartridge and mixing of the cartridge components. In contrast, smaller (e.g., fine) particles can have a very substantial effect on viscosity of a composition because of the high overall surface area that they provide. The use of larger (e.g., coarse) filler particles involves other tradeoffs as well. The resin and catalyst are delivered to the packaging (cartridge) through so-called fill tubes, which are sized to be accommodated with respect to the compartments of the cartridge. The fill tubes thus can only be of a certain diameter in order to be used in the cartridge manufacturing process. The internal diameter of the fill tubes limits the size of the filler particles that can be delivered through those tubes. Separately, when cartridges are clipped at either end during the manufacturing process to seal the resin and catalyst within the cartridge, larger diameter particles can interfere with the clips, causing leakage of resin or catalyst proximate the cartridge free ends and/or rupture of the cartridge when the cartridge is squeezed during installation of a clip. The use of larger diameter filler particles thus can result in a higher rejection rate of manufactured product due to quality control. For these reasons, it is known that clipping requirements are a limiting factor in the filler particle size used in grouting. Prior art compositions, for example, have had a maximum particle size of 3/16 inch. But even then, if a particle of such maximum size is present proximate a clip, the cartridge typically ruptures and has to be discarded rather than sold. It is for this reason that during cartridge manufacture, only a small percentage of larger (e.g., coarse) filler particles are used (e.g., 0-5%) such that the number of rejected cartridges due to leakage and/or rupture remains tolerable (e.g., 1-2%).
It also needs scarcely to be emphasized that rolling diaphragm piston pumps and progressive cavity pumps for pumping resin mastic and catalyst mastic during manufacture of the cartridges are extremely expensive, costing on the order of several hundred thousand dollars each not including regular maintenance costs.
One significant problem with the use of such pumps for delivering resin mastic through a filler tube to the compartment of a cartridge is that the pumps typically are operated proximate their highest rated pressure (e.g., 1,250 psi or 1,000 psi). At such an elevated pressure, the speed at which cartridges may be produced is significantly limited. Thus, there exists a need for methods and apparatuses for decreasing the pressure at which the resin mastic pumps are operated in connection with cartridge compartment filling and concomitantly for increasing the speed at which the cartridges may be produced.
The concept of adding a layer of lubricant around a plug flow of high viscosity material, such as sludge or concrete, to lower pumping pressure and provide increased capability of pumping the material greater distances at a given pressure is known for example from U.S. Pat. No. 5,361,797 to Crow et al. However, the challenges associated with a sludge pipeline lubrication system specifically involve issues of long distance transport rather than a problem associated with packaging a resin mastic let alone with a small diameter fill tube of changing cross-sectional shape (e.g., a portion of the length of the fill tube may have a circular cross-section while another portion may have a D-shaped cross-section; this is because of the shape of the shape of the compartment in the cartridge, as shown for example in U.S. Pat. No. 7,681,377 B2 to Simmons et al.). In yet another context, the outer surface of submarines may be lubricated by bubbles of hot air and oil vapor exhaust. But again, the challenges associated with moving a vessel the size of a submarine through the ocean are quite different from the problems associated with delivering resin mastic through a small diameter fill tube.
Given that the use of fillers was contemplated in resins for mine bolt grouting since at least the mid-1960s, e.g., as disclosed in U.S. Pat. No. 3,731,791 to Fourcade et al., there has been a long-felt but unsolved need for methods and apparatuses for decreasing the pressure at which the resin mastic pumps are operated in connection with delivering the resin mastic to the cartridge compartment and concomitantly for increasing the speed at which the cartridges may be produced.